Chips Metatronicos con luz y nanorods

Optical engineers at the University of Pennsylvania have created the first computer circuit where logic is performed with light instead of electricity. Dubbed “metatronics,” this light-based logic could enable smaller, faster, and more energy efficient computer chips.

The team, led by Nader Engheta, demonstrated that it’s possible to make resistors, inductors, and capacitors that act on light. By creating a chip that has a comb-like array of nanorods — tiny pillars of silicon nitride (pictured below) — the flow of light can be controlled in such a way that the “voltage” and “current” of the optical signal can be altered. By changing the height and width of the nanorods, and by altering their arrangement, different effects can be achieved. For example, if light has to pass by a short rod and then a tall rod, it might create a resistor-like effect — but a square of four short rods might act as an optical capacitor. The metatronic name comes from the fact that these nanorods are a metamaterial; a material that has has properties that can’t be found in nature.

Because Engheta and co are working with light instead of electricity, their metatronic chip has some very odd properties. For example, light’s polarization — whether the light wave undulates left/right or up/down — affects how it moves through the nanorods. When the light is aligned with the nanorods (pictured above), the circuit fires in parallel; but when light is perpendicular, the circuit is serial. In effect, one set of nanorods can act as two different circuits, which Engheta calls “stereo-circuitry.”

Furthermore, if you rotate the circuit itself through 45 degrees, the light wave would hit the nanorods obliquely, creating a circuit that is neither series or parallel — a setup that doesn’t occur in regular electronics. Eventually — and be careful, this might make your brain explode — you could even build 3D arrays of nanorods, where a single arrangement could act as dozens of different circuits.

To put this into perspective, imagine a low-power, ultra-high-speed CPU that turns into a GPU when you change the input signal — that’s the kind of functionality that metatronic circuits might one day enable. In the short term, though, work needs to be done on optical interconnects– and, as yet, the closest we’ve come to creating an optical transistor is MIT’s optical diode. In the short term it is much more likely that optoelectronic chips — chips that mix electronic logic with optical interconnects, and which can be built using standard semiconductor processes — will be used commercially.

Sebastian, A. (2012, February 24). Metatronic chip replaces electricity with light, swaps resistors with nanorods. Retrieved from www.extremetech.com/extreme/119759-metatronic-chip-replaces-electricity-with-light-swaps-resistors-with-nanor

Single-Atom Transistor Is End of Moore's Law; May Be Beginning of Quantum Computing

The smallest transistor ever built -- in fact, the smallest transistor that can be built -- has been created using a single phosphorus atom by an international team of researchers at the University of New South Wales, Purdue University and the University of Melbourne.

The single-atom device was described Sunday (Feb. 19) in a paper in the journal Nature Nanotechnology.
Michelle Simmons, group leader and director of the ARC Centre for Quantum Computation and Communication at the University of New South Wales, says the development is less about improving current technology than building future tech.
"This is a beautiful demonstration of controlling matter at the atomic scale to make a real device," Simmons says. "Fifty years ago when the first transistor was developed, no one could have predicted the role that computers would play in our society today. As we transition to atomic-scale devices, we are now entering a new paradigm where quantum mechanics promises a similar technological disruption. It is the promise of this future technology that makes this present development so exciting."
The same research team announced in January that it had developed a wire of phosphorus and silicon -- just one atom tall and four atoms wide -- that behaved like copper wire.
Simulations of the atomic transistor to model its behavior were conducted at Purdue using nanoHUB technology, an online community resource site for researchers in computational nanotechnology.
Gerhard Klimeck, who directed the Purdue group that ran the simulations, says this is an important development because it shows how small electronic components can be engineered.
"To me, this is the physical limit of Moore's Law," Klimeck says. "We can't make it smaller than this."
Although definitions can vary, simply stated Moore's Law holds that the number of transistors that can be placed on a processor will double approximately every 18 months. The latest Intel chip, the "Sandy Bridge," uses a manufacturing process to place 2.3 billion transistors 32 nanometers apart. A single phosphorus atom, by comparison, is just 0.1 nanometers across, which would significantly reduce the size of processors made using this technique, although it may be many years before single-atom processors actually are manufactured.
The single-atom transistor does have one serious limitation: It must be kept very cold, at least as cold as liquid nitrogen, or minus 391 degrees Fahrenheit (minus 196 Celsius).
"The atom sits in a well or channel, and for it to operate as a transistor the electrons must stay in that channel," Klimeck says. "At higher temperatures, the electrons move more and go outside of the channel. For this atom to act like a metal you have to contain the electrons to the channel.
"If someone develops a technique to contain the electrons, this technique could be used to build a computer that would work at room temperature. But this is a fundamental question for this technology."
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Journal Reference:

1. Martin Fuechsle, Jill A. Miwa, Suddhasatta Mahapatra, Hoon Ryu, Sunhee Lee, Oliver Warschkow, Lloyd C. L. Hollenberg, Gerhard Klimeck, Michelle Y. Simmons. A single-atom transistor. Nature Nanotechnology, 2012; DOI: 10.1038/nnano.2012.21

Nanowires.. the most easy way..

Nanowires are grown by a variety of mechanisms, including vapor-liquid-solid, vapor-quasiliquid-solid or vapor-quasisolid-solid, oxide-assisted growth, and self-catalytic growth (SCG) mechanisms. A critical analysis of the suitability of self-catalyzed nanowires, as compared to other nanowires, for next-generation technology development has been carried out. Basic causes of superiority of self-catalyzed (SCG) nanowires over othernanowires have been described. Polytypism in nanowires has been studied, and a model for polytypism has been proposed. The model predicts polytypism in good agreement with available experiments. 

This model, together with various evidences, demonstrates lower defects, dislocations, and stacking faults in SCG nanowires, as compared to those in other nanowires. Calculations of carrier mobility due to dislocation scattering, ionized impurity scattering, and acoustic phonon scattering explain the impact of defects, dislocations, and stacking faults on carrier transports in SCG and other nanowires. Analyses of growth mechanisms for nanowire growth directions indicate SCG nanowires to exhibit the most controlled growth directions. In-depth investigation uncovers the fundamental physics underlying the control of growth direction by the SCG mechanism. Self-organization of nanowires in large hierarchical arrays is crucial for ultra large-scale integration (ULSI). 

Unique features and advantages of self-organized SCG nanowires, unlike other nanowires, for this ULSI have been discussed. Investigations of nanowire dimension indicate self-catalyzed nanowires to have better control of dimension, higher stability, and higher probability, even for thinner structures.Theoretical calculations show that self-catalyzed nanowires, unlike catalyst-mediated nanowires, can have higher growth rate and lower growth temperature. Nanowire and nanotube characteristics have been found also to dictate the performance of nanoelectromechanical systems.Defects, such as stacking faults, dislocations, and nanopipes, which are common in catalyst-mediated nanowires and nanotubes, adversely affect the efficiency of nanowire (nanotube) nanoelectro-mechanical devices. The influence of seed-to-seed distance and collection area radius on the self-catalyzed, self-aligned nanowire growths in large arrays of seeds has been examined. 

A hypothesis has been presented for this. The present results are in good agreement with experiments. These results suggest that the SCG nanowires are perhaps the best vehicles for revolutionary advancement of tomorrow's nanotechnology. 

One of the newest application of this is in the batteries. Higher-density batteries, more efficient thin-film solar cells, and better catalysts may all soon be possible, thanks to a new technique that allows nanowires to be “decorated” with nanoparticles. Using the novel technology, scientists from Stanford University have been able to festoon the outside surfaces of nanowires with intricate chains of metal oxide or noble metal nanoparticles, thereby drastically boosting the effective surface area of the nanowires. Other researchers have previously tried to achieve the same end result, but apparently never with such success.

reference:

Noor Mohammad, S. S. (2011). Why self-catalyzed nanowires are most suitable for large-scale hierarchical integrated designs of nanowire nanoelectronics. Journal Of Applied Physics, 110(8), 084310. doi:10.1063/1.3624585

http://www.gizmag.com/decorated-nanowires-better-batteries/22369/

Nano-PLAYERAS!!

No dejes pasar la oportunidad de poseer un pedazo de historia!

Ya están disponibles para apartar las camisetas alegóricas a NANOUDLAP, diseñadas por NANOSapiens, la organización estudiantil en pro-de la comprensión pública de la Nanotecnología en nuestra institución. Por solo $80.00 (ochenta pesos) tu puedes apartar una, dos, tres...las que desees, para usar, regalar el día de la Madre, del Padre o en Navidad, o simplemente para presumir.

Para apartar, comprar, pedidos, etc, contacta a Oscar Jimenez (oscar.jimenezgo@udlap.mx) y forma parte de un grupo selecto de orgullosos estudiantes de Nanotecnología e Ingeniería Molecular que la lucirán brevemente.

Go Nano!

Moduladores Opticos de Grafenos

Scientists at the University of California, Berkeley, have demonstrated a new technology for graphene that could break the current speed limits in digital communications.

The team of researchers, led by UC Berkeley engineering professor Xiang Zhang, built a tiny optical device that uses graphene, a one-atom-thick layer of crystallized carbon, to switch light on and off. This switching ability is the fundamental characteristic of a network modulator, which controls the speed at which data packets are transmitted. The faster the data pulses are sent out, the greater the volume of information that can be sent. Graphene-based modulators could soon allow consumers to stream full-length, high-definition, 3-D movies onto a smartphone in a matter of seconds, the researchers said.

Schematic illustration of the graphene-based optical modulator. A layer of graphene (black fishnet) is placed on top of a silicon waveguide (blue), which is used as an optical fiber to guide light. Electric signals sent in from the side of the graphene through gold (Au) and platinum (Pt) electrodes alter the amount of photons the graphene absorbs. (Ming Liu graphic)

“This is the world’s smallest optical modulator, and the modulator in data communications is the heart of speed control,” said Zhang, who directs a National Science Foundation (NSF) Nanoscale Science and Engineering Center at UC Berkeley. “Graphene enables us to make modulators that are incredibly compact and that potentially perform at speeds up to ten times faster than current technology allows. This new technology will significantly enhance our capabilities in ultrafast optical communication and computing.”

In this latest work, described in the May 8 advanced online publication of the journalNature, researchers were able to tune the graphene electrically to absorb light in wavelengths used in data communication. This advance adds yet another advantage to graphene, which has gained a reputation as a wonder material since 2004 when it was first extracted from graphite, the same element in pencil lead. That achievement earned University of Manchester scientists Andre Geim and Konstantin Novoselov the Nobel Prize in Physics last year.

Zhang worked with fellow faculty member Feng Wang, an assistant professor of physics and head of the Ultrafast Nano-Optics Group at UC Berkeley. Both Zhang and Wang are faculty scientists at Lawrence Berkeley National Laboratory’s Materials Science Division.

“The impact of this technology will be far-reaching,” said Wang. “In addition to high-speed operations, graphene-based modulators could lead to unconventional applications due to graphene’s flexibility and ease in integration with different kinds of materials. Graphene can also be used to modulate new frequency ranges, such as mid-infrared light, that are widely used in molecular sensing.”

Graphene is the thinnest, strongest crystalline material yet known. It can be stretched like rubber, and it has the added benefit of being an excellent conductor of heat and electricity. This last quality of graphene makes it a particularly attractive material for electronics.

“Graphene is compatible with silicon technology and is very cheap to make,” said Ming Liu, post-doctoral researcher in Zhang’s lab and co-lead author of the study. “Researchers in Korea last year have already produced 30-inch sheets of it. Moreover, very little graphene is required for use as a modulator. The graphite in a pencil can provide enough graphene to fabricate 1 billion optical modulators.”

It is the behavior of photons and electrons in graphene that first caught the attention of the UC Berkeley researchers.

The researchers found that the energy of the electrons, referred to as its Fermi level, can be easily altered depending upon the voltage applied to the material. The graphene’s Fermi level in turn determines if the light is absorbed or not.

When a sufficient negative voltage is applied, electrons are drawn out of the graphene and are no longer available to absorb photons. The light is “switched on” because the graphene becomes totally transparent as the photons pass through.

Shown is a scanning electron microscope (SEM) image magnifying the key structures of the graphene-based optical modulator. (Colors were added to enhance the contrast). Gold (Au) and platinum (Pt) electrodes are used to apply electrical charges to the sheet of graphene, shown in blue, placed on top of the silicon (Si) waveguide, shown in red. The voltage can control the graphene's transparency, effectively turning the setup into an optical modulator that can turn light on and off. (Ming Liu image)

Graphene is also transparent at certain positive voltages because, in that situation, the electrons become packed so tightly that they cannot absorb the photons.

The researchers found a sweet spot in the middle where there is just enough voltage applied so the electrons can prevent the photons from passing, effectively switching the light “off.”

“If graphene were a hallway, and electrons were people, you could say that, when the hall is empty, there’s no one around to stop the photons,” said Xiaobo Yin, co-lead author of the Nature paper and a research scientist in Zhang’s lab. “In the other extreme, when the hall is too crowded, people can’t move and are ineffective in blocking the photons. It’s in between these two scenarios that the electrons are allowed to interact with and absorb the photons, and the graphene becomes opaque.”

In their experiment, the researchers layered graphene on top of a silicon waveguide to fabricate optical modulators. The researchers were able to achieve a modulation speed of 1 gigahertz, but they noted that the speed could theoretically reach as high as 500 gigahertz for a single modulator.

While components based upon optics have many advantages over those that use electricity, including the ability to carry denser packets of data more quickly, attempts to create optical interconnects that fit neatly onto a computer chip have been hampered by the relatively large amount of space required in photonics.

Light waves are less agile in tight spaces than their electrical counterparts, the researchers noted, so photon-based applications have been primarily confined to large-scale devices, such as fiber optic lines.

“Electrons can easily make an L-shaped turn because the wavelengths in which they operate are small,” said Zhang. “Light wavelengths are generally bigger, so they need more space to maneuver. It’s like turning a long, stretch limo instead of a motorcycle around a corner. That’s why optics require bulky mirrors to control their movements. Scaling down the optical device also makes it faster because the single atomic layer of graphene can significantly reduce the capacitance – the ability to hold an electric charge – which often hinders device speed.”

Graphene-based modulators could overcome the space barrier of optical devices, the researchers said. They successfully shrunk a graphene-based optical modulator down to a relatively tiny 25 square microns, a size roughly 400 times smaller than a human hair. The footprint of a typical commercial modulator can be as large as a few square millimeters.

Even at such a small size, graphene packs a punch in bandwidth capability. Graphene can absorb a broad spectrum of light, ranging over thousands of nanometers from ultraviolet to infrared wavelengths. This allows graphene to carry more data than current state-of-the-art modulators, which operate at a bandwidth of up to 10 nanometers, the researchers said.

“Graphene-based modulators not only offer an increase in modulation speed, they can enable greater amounts of data packed into each pulse,” said Zhang. “Instead of broadband, we will have ‘extremeband.’ What we see here and going forward with graphene-based modulators are tremendous improvements, not only in consumer electronics, but in any field that is now limited by data transmission speeds, including bioinformatics and weather forecasting. We hope to see industrial applications of this new device in the next few years.”

Other UC Berkeley co-authors of this paper are graduate student Erick Ulin-Avila and post-doctoral researcher Thomas Zentgraf in Zhang’s lab; and visiting scholar Baisong Geng and graduate student Long Ju in Wang’s lab.

This work was supported through the Center for Scalable and Integrated Nano-Manufacturing (SINAM), an NSF Nanoscale Science and Engineering Center. Funding from the Department of Energy’s Basic Energy Science program at Lawrence Berkeley National Laboratory also helped support this research.

Yang, S. (2011, May 08). Graphene optical modulators could lead to ultrafast communications. Retrieved from newscenter.berkeley.edu/2011/05/08/graphene-optical-modulators-ultrafast-communications/

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Self-Assembling Nanorods

Researchers Obtain 1-, 2 And 3-D Nanorod Arrays and Networks.

Abraham Mauleon Amieva

A relatively fast, easy and inexpensive technique for inducing nanorods -- rod-shaped semiconductor nanocrystals -- to self-assemble into one-, two- and even three-dimensional macroscopic structures has been developed by a team of researchers with the U.S. Department of Energy (DOE)'s Lawrence Berkeley National Laboratory (Berkeley Lab). This technique should enable more effective use of nanorods in solar cells, magnetic storage devices and sensors. It should also help boost the electrical and mechanical properties of nanorod-polymer composites.


Leading this project was Ting Xu, a polymer scientist who holds joint appointments with Berkeley Lab's Materials Sciences Division and the University of California (UC) Berkeley's Departments of Materials Sciences and Engineering, and Chemistry. Xu and her research group used block copolymers -- long sequences or "blocks" of one type of monomer bound to blocks of another type of monomer -- as a platform to guide the self-assembly of nanorods into complex structures and hierarchical patterns. Block copolymers have an innate ability to self-assemble into well-defined arrays of nano-sized structures over macroscopic distances.

"Ours is a simple and versatile technique for controlling the orientation of nanorods within block copolymers," Xu says. "By varying the morphology of the block copolymers and the chemical nature of the nanorods, we can provide the controlled self-assembly in nanorods and nanorod-based nanocomposites that is critical for their use in the fabrication of optical and electronic devices."

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La Nanotecnologia se disfraza de Virus.

Qdots are tiny fluorescent particles, smaller than a virus, and over 1000 times smaller than a cell, which can be linked to biological molecules, such as antibodies. Once linked, the fluorescence would make it easy to find which cells contain the protein the antibody recognizes, and where in the cell this protein is located. However there have been problems getting the Qdots into cells without them clumping, or being packaged in to endosomes, and excreted from the cells as waste.

Researchers from the City College of New York have overcome this problem by coating the Qdots in lipid and protein coats based on Sendai virus. Prof Maribel Vazquez explained, "While cells have complex defense mechanisms to protect themselves against attack, viruses have evolved ways to fool the cell into letting them in. We were able to exploit these mechanisms by fusing inactivated mouse parainfluenza virus with liposomes containing Qdots. The Qdots were in turn attached to an antibody against EGFR. So, once inside the cell, the Qdot-antibody complexes were able to bind to the receptor and the amount of bound complex could be monitored by measuring Qdot fluorescence."

This study looked at the level of EGFR as a marker for cancer but the Qdots could be attached to any antibody. Antibody-Qdot sets would allow rapid identification of different cancer types ,determine potential chemotherapy resistance, and lead a more individualized treatment plan.

More information: Sendai Virus-based Liposomes Enable Targeted Cytosolic Delivery of Nanoparticles in Brain Tumor-Derived Cells Veronica Dudu, Veronica Rotari and Maribel Vazquez. Journal of Nanobiotechnology (in press)

Biomed Central, E. (2012, February 17). Nano-technology uses virus' coats to fool cancer cells. Retrieved from www.physorg.com/nanotech-news/bio-medicine/

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Reconstruyendo el Cuerpo una Molécula a la vez.

Making paralyzed mice walk was just the first step for Samuel Stupp. Now he and his team are on a mission to help our bodies repair themselves.

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Bionanotech Guru: "I have an interdisciplinary brain," Samuel Stupp says. | Photograph by Tim Klein

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In The Clean Room: Dorota Rozkiewicz, a materials scientist, is now working with biologists. | Photograph by Tim Klein

Samuel Stupp didn't trust his eyes.

The mice in the video flickering on his colleague's computer screen were moving their legs. Their back feet trailed behind them from time to time, but the fact that they were walking at all was astounding. Only a few weeks earlier, they'd been paralyzed from the waist down. Then Stupp's team at Northwestern University injected them with made-to-order molecules. Now the mice were trying to run around their cage. "I wasn't satisfied with the video, so I went to the lab to see it myself," remembers Stupp. "I was totally stunned."

Those mice were the first living glimpse of the future that Stupp is hoping to accelerate in his role as the director of the Institute for BioNanotechnology in Medicine at Northwestern. It's a future in which molecular self-assembly -- where researchers direct molecules to spontaneously combine into ordered structures -- will help the body heal itself. The prospect is straight out of The Six Million Dollar Man, but one better, since damaged parts will be replaced with actual human tissue instead of metal.

The intrepid Stupp, 61, first made his name as a materials scientist in the highly technical field of self-assembly, which has traditionally involved developing products for industrial use -- a computer chip, for example, or a protective coating. But back in the late '90s, when "regenerative medicine" still sounded like something from a sci-fi novel, he began to wonder if he might be able to apply the principles of molecular self-assembly to biology. "I have an interdisciplinary brain," Stupp says in a lilting in-between accent (born in Costa Rica, he speaks four languages fluently). "We had this idea that you could have a single platform that would cover an extremely broad range of conditions.

"It's always easier when you specialize in something, and there is a place for that," he continues. "But if you're trying to solve these kinds of problems, you cannot do it without interdisciplinary research." So he has built a lab in his own image, boasting biologists, physicists, chemists, and nanotechnologists, as well as materials scientists; he has also forged partnerships with neuroscientists and surgeons.

With his shiny bald pate and unflinching gaze, Stupp reminds me of actor-producer Bruce Willis, and when he says he'd want to make movies if he weren't a scientist, it makes sense. It's the directorial thrill of fitting the right puzzle pieces together, the synergy of assembling a diverse team and watching the sparks fly, that appeals to him. "You can motivate and inspire people to a higher level of creativity. I guide the process, give the 35,000-foot view."

The potential of that process is breathtaking. One day, the specialized molecules -- the "noodle gels" and macroscopic scaffolds -- that Stupp and his team are creating could repair injured spinal cords and treat brain disorders. Success would mean better lives for countless patients and enormous profits for Nanotope, the startup Stupp founded to commercialize the lab's discoveries. And even failed ideas can serendipitously turn into better ones. "When you see something interesting, you have an idea what might happen," Stupp says, "but you might discover something completely orthogonal that you didn't predict."

The Institute for Bionanotechnology in Medicine (IBNAM) takes up the 11th floor of the towering Robert Lurie Medical Center at Northwestern's downtown Chicago campus, just steps from the shore of Lake Michigan. When I arrive, Stupp is running late, so Dorota Rozkiewicz, one of his junior colleagues, gives me a whirlwind lab tour, complete with superlatives about her boss. "He does great science, but many people are innovative," she tells me conspiratorially, between spiels about the state-of-the-art mass spectrometer and the clean room. "He also has this vision of where the work is going -- which subjects will be a great success in the future."

Rozkiewicz and I are still chatting in a conference room overlooking the lakeshore neighborhood when Stupp enters, so soundlessly that I don't realize he's there. He typically works on dozens of projects at any one time, but he doesn't seem stressed, or rushed. Instead, he fetches me a bottle of water and insists I tell him how I got into writing. It's only when he starts talking about what motivates him that I get a real sense of the magnitude, the ambition, of his self-imposed mission. "I don't like the idea of applied research -- develop a product and that's your focus," he says, looking straight at me without hesitation. "I want to leave behind a scientific legacy that can be used by other people in other fields."

Stupp didn't always have such a strong sense of his scientific calling. He grew up in Costa Rica, where his Eastern European parents had fled after Hitler rose to power, went north to attend UCLA, and then pursued a materials-science PhD at Northwestern. It seemed a practical choice, since he was hoping to go back to Costa Rica someday and he knew the country's economic situation was shaky.

Shovoda, E. (2011, February 07). How samuel stupp is rebuilding your body, one molecule at a time. Retrieved from http://www.stumbleupon.com/su/1GQni

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